Fuel level indicator system



Jan. 18, 1949. D. B. BROWNE 2,459,261

FUEL LEVEL INDICATOR SYSTEM Filed Feb. 2, 1946 fill enter DON/4L0.B'NN/ON EEOWNE Patented Jan. 18, 1949 FUEL LEVEL INDICATOR SYSTEM DonaldBennion Browne, Harpenden, England, asslgnor to General MotorsCorporation, Detroit, Mich., a corporation of Delaware ApplicationFebruary 2, 1946, Serial No. 645,219 In Great Britain February 15, 19453 Claims. (01. 177-311) This invention relates to electric lamps used asindicators.

Such lamps are often 'used to indicate a definite factor, such astemperature, pressure, quantity. flow and the like which is apt tofluctuate about a steady state condition.

It is undesirable that the lamp should flicker when the factor is in afluctuating condition, but it should change when there is a definitechange beyond the critical point. Any fluctuation is usually emphasisedby the sensitiveness of the control device such as the thermostat,diaphragm, float or metering device, whatever is used. Any reduction insensitivity involves likelihood of sluggishness of response or inabilityto keep within critical limits.

These difiiculties are overcome by this invention according to which thefilament is associated with a heat accumulator having a rate ofdissipation approximately the same as the rate of heat generation of thefilament under steady state conditions.

Use for this purpose can be made of a refractory material in contactwith the filament such that theheat generated by the transient currentdue to fluctuations heats up the material but does not light up thefilament.

Further features of the invention will be apparent from the followingdetailed description of one embodiment and one application thereof,reference being made to the accompanying drawings in which:

Figure 1 shows one form of electric lamp in accordance with theinvention; and

Figure 2 shows diagrammatically an indicator system using a lampaccording to the invention, for a fuel tank on a motor vehicle.

As shown in Figure 1 the lamp i has a filament 2 which is coiled arounda cylinder 3 of heat dissipating material formed of ceramic materialincluding a substantial percentage of refractory oxides. One suitablecomposition is as follows:

Per cent China clay 43 Ball clay 12 Glass 5 Synthetic sillimanite 40Whatever mixture is chosen for this purpose will be such that there willbe no dissociation, and consequent deposition on the glass, due to heat.

The filament supports 4, 5 are suitably strengthened to hold thematerial. If desired the the requisite thermal capacity and dissipationthe filament will not glow persistently until a sufficiently steadycurrent flows.

In applying the invention as shown in Figure 2 to indicate a liquidquantity, for example, the

minimum quantity of fuel in a fuel tank 6 of an internal combustionengine, the float I operates in the usual way an arm 8 controlling avariable resistance 9 in a circuit from battery I0 to ground through agalvanometer indicator l l and the ignition switch I2. As the float Isinks, the arm 8 moves clockwise and decreases the amount of resistance9 in the circuit, and accordingly the indicator II shows the fall inliquid level. As the liquid level falls to a critically empty level thearm 8 moves towards the dotted line position, closer to the fixedcontact l3 in the circuit of lamp I, until finally the spring contact l4on arm 8 completes the circuit. Due to movement of the vehicle, thefioat 1 moves up and down and. the contact is intermittent. Consequentlythe lamp I does not light up. When the liquid level falls such thatmovement does not affect the contact, a steady current flows and thelamp I gives indication that the critically low level has been reached.

In a normal system, as the liquid level approaches the critical value,its swirling normally causes an intermittent operation of the switch andconsequently a flickering of the light. By partially or completelyembedding or winding the lamp filament in or on a piece of refractorymaterial of the requisite thermal capacity and dissipation, the filamentwill not glow persistently until a sufficiently steady current flows dueto a steady state condition of liquid level.

It is clear that such a lamp can be used in any indicator installationadapted to indicate any of the factors above indicated.

I claim:

1. An electrical indicator system for a variable factor which is subjectto fluctuations about a median quantity condition, comprising a devicemovable in accordance with said fluctuations, an electrical circuitwhose continuity may be inter rupted by said device in accordance withsaid fluctuations, and in said circuit an indicator lamp whose filamentis in heat conductive relation with a heat dissipator such that thefilament does not light up until said median quantity of said variablefactor reaches a predetermined value.

2. An electrical indicator system for a fuel tank for aninternal-combustion engine comprising a float in said tank, an electriccircuit, contacts in said circuit controlled and adapted to be closed bysaid float when a low fuel level is 3 reached in said tank. and anelectrical indicator lamp in said circuit said lamp having a filamentand a heat dissipating mass in contact therewith such that the filamentlights up only when said contacts are firmly and completely closed bysaid float.

3. In an electrical indicating system for a liquid level which issubject to fluctuations about a steady state condition, comprising afloat movable in accordance with the fluctuations, an electrical circuitincluding an indicator la mp the continuity of which is determined bythe position of said float and said indicator lamp having a filament inheat conductive relation with a heat dissipator of such thermo capacitythat the filament does not light up until the median value of saidfluctuation of the liquid level is below a predetermined position.

DONALD BENNION BROWNE.

REFERENCES CITED The foilowingireferences are of record in the flle ofthis patent:

5 UNITED STATES BA'I'ENTS Number Name Date 1,607,512 Churcher et al Nov.16, 1926 1,749,1'36 Heany Mar. 4, 1930 1 7 ,4 9 Braselton Oct. 2, 1934UNITED STATES PATENTS Number Country v Date 15,514 Great Britain 1903

